High speed sailboat

ABSTRACT

The present invention is directed to a high speed sailboat which uses a horizontal, downward pulley hydrofoil which is extended from the hull on the windward side to provide a stabilizing moment equal and opposite to the sail heeling moment.

United States Patent [1 1 Shutt Oct. 2, 1973 [5 1 HIGH SPEED SAILBOAT 3,112,725 12/1963 Malrose 114/39 2,139,303 12 1938 G 114 66. [76] inventor: Sidney c. Shutt, 612 Briarwood m, I I 5 H Brea Primary Examiner-Duane A. Reger [22] Filed: Sept. 9, 1971 Assistant ExaminerJesus D. Sotelo Appl. No.: 179,068

US. Cl 114/39, 114/665 H, 114/122 Int. Cl B63h 9/04 Field of Search 114/39, 66.5 H, 12l123 References Cited UNITED STATES PATENTS 11/1966 Nason 114/665 H Att0rneyDominick Nordelli [57] ABSTRACT The present invention is directed to a high speed sai1 boat which uses a horizontal, downward pulley hydrofoil which is extended from the hull on the windward side to provide a stabilizing moment equal and opposite to the sail heeling moment.

7 Claims, 17 Drawing Figures Pmmmw 2 SHEET 10F 5 IN VENTOR 5/0/10. Y 6. 57/077 oQwamQ DM M/ ATTORNEY PATENTEDBET m saw u or s INVENTOR S/DIVIE Y 6': 57/4/77- I ATTORNEY PATENTED w 2'91:

SHEET 5 0F 5 INVENTOR. SYDNEY 6'. 57/077 [ZMWKD M ATTU/Q/VEV 1 HIGH SPEED SAILBOAT BACKGROUND OF THE INVENTION The invention pertains to the field of high speed sailboats and more particularly to the field of sailboats using hydrofoil sections.

All sailboats provide in their design and construction a means for producing a counter heeling moment to prevent the sail force from capsizing the craft. The conventional approach to achieve a counter heeling'moment is to allow the separation between the crafts center of mass and center of buoyancy to continuously vary to provide an equal and opposite moment to the sail heeling moment. Several variations of positioning the center of mass of the boat with respect to the center of buoyancy have evolved over many years. The single hull craft, with weighted keel, represents the conventional concept of sailboat roll stability. Improvements have been made to gain a wider mass-buoyancy separation by increasing the keel weight, by the crew hiking out over the rail, and by using a trapeze to allow a crew member to hike out beyond the rail. The multihull crafts achieve greater counter heeling moments by using greater separation of the mass center and the buoyancy center, but the basic idea is the same. These crafts have evolved into catamarans, Outriggers, trimarans, and proas. All of these can be made light, with samll displacement hulls having low drag. These boats have a large counter heeling moment which allows the use of larger sails; therefore, very fast boats have been made of these types.

Two or more hulls have the disadvantage that they cost more and although their drag is low it would be even lower if only one hull having a low drag were used. Also, all of the designs presently on the market use a mass displaced from the center of buoyancy to achieve stability; this places a limit on the wind velocity in which the craft can be sailed without capsizing.

It would therefore be highly desirable to have a maneuver-able. controllable, low drag boat wherein a heeling counter force would be created without adding a mass to create the counter force. It would also be highly desirable to have a boat wherein the counter heeling force would increase as the wind pressure on the sails increased and the speed of the boat increased. The present invention achieves these desirable results.

SUMMARY OF THE INVENTION The present invention is comprised of a sailboat having at least one hull, a horizontal tin, and means for supporting the horizontal fin from the windward side of the boat such that the fin rides below the surface of the water and changes its angle of incidence to compensate for increasing or decreasing heeling forces acting on the hull. A planing surface extends forward of the horizontal fin and is fixedly attached to the horizontal fin. The planing surface is designed to ride on the water surface and to follow the water surface contour. A ver tical fin is affixed to the rear of the horizontal fin to force the planing surface to remain in front of the horizontal fin. A second smaller horizontal fin and vertical rudder may be affixed to the entire assembly further back to force the planing surface into contact with the water surface and to aid in maintaining the planing surface forward of the horizontal fin. In addition, a holddown horizontal fin may be mounted to the underside of the planing surface to hold the planing surface in contact with the water surface under rough water con ditions. One of these fin assemblies may be mounted to the sailboats hull in a temporary manner so that it can be shifted to extend from the windward side of the hull.

On larger hulls where it would be inconvenient to keep shifting the tin assembly back and forth, two assemblies can be attached to the hull in such a manner that each one can be pulled from the water when not in use so as to minimize drag and to prevent fouling.

From the foregoing it can be seen that it is an object of the present invention to provide an improved high speed sailboat.

It is another object of the present invention to provide a sailboat with a holddown foil section that counteracts the heeling forces on the boats sails.

It is another object of the present invention to provide a high speed sailboat having an extendible foil section that exerts a varying force on the sailboat which force is proportional and opposite to the force acting on the sails. 1

It is a further object of the present invention to provide a holddown fin for a high speed sailboat which fin changes its angle of incidence in proportion to the upward force exerted on the fin. 1 t

These and other objects of the present invention will become more apparent when taken in conjunction with the following description and drawings, throughout which like characters indicate like parts, and which drawings form a part of this application.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of one embodiment of the'present invention showing force vectors which operate on the boat;

FIG. 2 is a front view of the present invention illustrating the force vectors which typically operate on the boat;

FIG. 3 is a perspective view of the holddown fin assembly of the present invention; 1

FIG. 4 is a side view of the holddown fin assembly;

FIG. 5 is a top view of the holddown fin assembly FIG. 6 is a front view of the holddown fin assembly;

FIG. 7a, 7b, and 7c are section views taken from FIGS. 4 and 5 along section lines 7a-7a, 7b7b, and 7c7c respectively; I

FIG. 8a, 8b, 8c, and 8d illustrate the angle ofincidence of theholddown fin with respect to the water surface for differentpulls for the same hull speed;

FIG. 9 is a perspective view of a second embodiment of the present invention;

FIG. 10 is ,a perspective view of a third embodiment of the present invention;

FIG. I1 is a side viewof a planing surface which may be used with the holddown fin; and

FIG. 12 is a top view of the planing surface of FIG. 1 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, the unimaran sailboat 10 uses a single slim hull 11 from whichextends upwards a mast 13 for supporting a sail l2. A centerboard 16.extends from the bottom of the hull to minimize the leeward movement of the hull through the water 17. A hiking board 14 provides a seat for the helmsman and also allows the helmsman to add his weight to the counter heeling force. Attached to the hiking board 14 is a fin supporting assembly which is also connected to the mast 13 by means ofa guy cable 18. A holddown fin is gimbaled to the supporting assembly 15 and creates a downward force F,- when the hull ll moves through the water 17. This downward force is transmitted to the hull through the cable 18 and mast 13. The craft is balanced about its heeling axis (ROLL) by adjusting the downward force F, to balance the following equation:

Hh W] a F b (I) wherein H is the force vector of the wind on sail 12; h is the height between the sail force vector and centerboard lateral force vector; W, is the weight of the helmsman, a is the distance that the helmsman is from the vessels center of buoyancy; F, is the downward force exerted by the fin 20 and; b is the distance between fin 20 and the vessels center of buoyancy. From equation I it can be seen that as H increases or decreases, F, must also increase or decrease in order to eliminate rolling about the hulls roll axis. The centerboard 16 exerts a counter force F to the side pressure H of the wind to minimize leeway but, except for preventing rolling motions caused by short quick bursts of wind, the centerboard will not counteract the steady pressure of the wind.

The holddown fin 20 is used to create the variable force F, which counteracts the varying heeling force H. Steering is accomplished with the aid of a rudder 19.

Referring to FIG. 3, the holddown fin assembly 20 is affixed to the fin supporting assembly 15 by means of a gimbal which allows the fin assembly to rotate about the pitch and yaw axis. The fin assembly is comprised of an elongated body member 23. Pivotaly affixed to the forward end of the body member is a planing surface 24. Connected to the opposite end of body member 23 is a vertical rudder 28 which tends to maintain the planing surface 24 forward of the supporting assembly 15. A horizontal hydrofoil section 27 is affixed to the same end as rudder 28. A vertical fin 22 also acts as a rudder and in addition provides structural support for the main horizontal inverted hydrofoil 21.

In operation the holddown fin converts forward to a downward force which is equal to the upward pull on the holddown fin. The inverted hydrofoil 21 is used to produce the downward force.

Referring to FIGS. 3, 4, 5, and 6 in conjunction with each other, the planing surface 24 is designed to float at low speeds and plane at high speeds on the surface of water 17. When the boats hull is in forward motion the forward motion is transmitted to the holddown fin which results in forces acting on the rudder 28 and the vertical fin 22 to rotate the fin assembly about the yaw axis so that the planing surface is riding at the front and on the surface of the water. Because the pitch axis is behind the foil vertical force line of action 29, a moment is produced when the body 23 is pulled upward. This moment is with respect to the planing surface which remains on the water surface. The moment causes a pitch rotation that forces the foil angle of incidence a to increase. An increase in incidence angle causes an increase in foil downward forces until an equal and opposite force is generated to offset the upward pull. If the pull is decreased. the foil force pulls the foil deeper. reducing the incidence angle until equilibrium is again reached.

FIG. 7b illustrates the symmetrical cross-sectional shape of vertical fin 22. FIG. 70 illustrates the foil section of the horizontal fin 27. The foil is designed to give an upward lift to the end of member 23 when it is run through the water with a forward motion. FIG. 7a illustrates the foil section of the inverted hydrofoil 21. Othe cross section is designed to create a downward force for a forward motion of the fin.

Referring now to FIGS. 81;, 8b, 8c", and 84; FIG. 8a illustrates the position of the holddown fin assembly 20 for an upward force condition; in this position the incidence angle a is 4 and the rearmost horizontal fin 27 is positioned below the water surface. In this position the rear fin has an incidence angle a set at 1 which is sufficient to produce an upward force which applies a moment greater and in the opposite direction than the moment sida'uea'ty" the hydrofoil 21. The result is that the planing surface is forced to remain on the water surface. In this position the holddown fin will produce a downward force P=0.016 v where P is in pounds and v, the velocity, is in ft/sec. FIG. 8b illustrates the holddown fin position for a moderate upward pull. The horizontal fin 27 is above the surface of the water and the angle of incidence of fin 2 1 i s at a f 1 In this position the upward pull is P 0.177 v In FIG. 8c the position for a larger pull is shown. The angle incidence is a 6 and for this position P 0.376 v In FIG. 8d the upward pull is 0.566 v and the angle a is 1 1".

The water surface has been depicted as being flat; in actuality when the wind is up the surface is not flat.

' Therefore, from time to time the planing surface 24 attempts to leave the water surface. At these times, horizontal fin 27 either simultaneously or shortly thereafter is forced below the water surface and by its forward motion through the water it is forced to quickly move upwards effectively forcing the planing surface downward back into contact with the water surface.

FIG. 9 illustrates a second embodiment of the invention wherein the hull 11 is provided with a planing surface 30 which is affixed to the hull with support brackets 33. The support bracket is pivoted at a-a l and is raised and lowered by the pull of line 34. A vertical fin 32 supports a larger horizontal foil 31. The hiking board 14, support 15, and holddown assembly 20 remain the same as for the prior embodiment. The operation is the same as the prior embodiment for moderate speeds. -At sufficient speed, the bow planing surface 30 is lowered by pulling line 34 which causes the bow of the hull 11 to pitch up. This action increases the angle ofincidence of the main foil 31 which sharply increases its lift necessary to force the entire craft out of the water. The friction between the hull and water is greatly decreased resulting in a significant increase in speed. Considerable kinetic energy is available in the start of a turn when coming about. There are two additional factors which contribute to fast and complete come abouts; these are (a) the low resistance to turning as a result of the centrally located main foil and the selfsteering action of the holddown fin and bow planing surface and (b) the conversion of potential energy to kinetic energy as the craft glides down into the water at the end of turn tends to maintain the crafts forward motion until the turn is complete. When operating on the foil at high speed and desiring to operate in the dis- .controlled.

A third embodiment of the invention is disclosed in FIG. 10. The hull 11 is fitted with outrigger hulls 40 and i tion is near zero. Whenoperating at forward speeds,.

the floats are out of the water and serve no function. The seat 14 is mounted between the supports 42 and 43. The supporting assembly 15 is affixed to the supports 42 and 43 as in the previously described embodiments with the holddown fin affixed to the supporting assembly. This embodiment also can include the central lifting hydrofoil and bow planing surface. Again the side floats are used only at near zero speeds. As previously stated, two holddown fins and support assemblies can be used, one on each side. When using one assembly and holddown fin they can be shifted to the opposite side of the hull when needed. Also, the holddown fin assembly can be left on one side for both tacks; upwind on one tack as described and downwind on the other tack. The helmsmans heeling moment must be greater than the sail heeling moment in this case. i

Referring now to FIGS. 11 and 12, the planing surface 24 is shown pivotly mounted to the forward endof body member 23 by means of a vertical fin assembly 46 and pivot pin 48. The vertical fin assembly has a symmetrical cross section of the type shown in FIG. 7b. The upper end of the fin assembly 45 is round and fits within a bushing 44. Bushing 44 is fixedly attached to body member 23 which allows the planing surface 24 and the fin 45 to rotate in yaw. A slot 50 in the planing surface 24 provides a clearance so that the planing surface can move in pitch about the pivot pin 48. An in-' verted horizontal foil 47, identical in cross section to the foil shown in 7a, is fixedly attached to the bottom of the vertical fin assembly 46 at an angle aso asto produce a downward force F, proportional to the product of d and the square of the forward velocity v. The planingsurface itself produces an upward force F Attached to the rear of the planing surface is a rudder 49. Rudder 49 forces the planing surface and the vertical fin 46 to point forward when moved through the water. This arrangement provides a positive downward force to the planing surface forcing the planing surface to ride on a very rough water surface.

Although the invention has been described in terms of the preferred embodiments, the scope of the invention is limited only by the breadth of the attached claims. I

l claim:

1. In combination:

a sailboat having a hull and a sang a supporting assembly fixed to said hull-and projecting from the windward'side of said hull; and

a hold-down fin assembly comprising:

an elongated body member pivotably depending from said supporting assembly and disposed to pivot freely about a yaw axis and a pitch axis,

a planing surface depending from said body member at the forward end thereof,

a hold-down fin fixed and depending from said body member aft of said planing surface and disposed transversely to said body member, and

first means fixed to said body member and responsive to the forward motion of said sailboat to maintain said planing surface forward of said hold-down fin.

2. The combination of claim 1 wherein means are provided responsive to the forward motion thereof to maintain said planing surface in contact with the water.

3. The combination of claim 1 wherein said first means includes a vertical fin connected between said hold-down fin and said body member.

4. The combination of claim 3 wherein: means are provided responsive to the forward motion thereof to maintain said planing surface in contact with the water, and

increase the pulldown force.

5. The combination of claim 4 wherein a lifting fin is disposed depending from said body member aft of said hold-down fin and disposed, in response to the forward motion thereof, to lift the aft end of said body member to maintain said planing surface in contact with the water. I

6. The combination of claim 1 wherein:

second means are pivotably mounted onto the forward end of said hull and disposed to pivot downward about another pitch axis; I H another planing surface is mounted to the underside of said second means so that, as said second means .is pivoted downward, said other planing surface forces the forward end of the hull upwards; and

a transverse fin, fixed to said hull, to pivot with said hull as it pitches and disposed to be responsive to the forward motion of said hull, to lift the aft end to said hull whenever the forward end thereof is lifted.

7. The combination of claim 6 wherein a vertical fin is fixed to the under side of said hull and said transverse fin is fixed to said vertical fin below the hull. 

1. In combination: a sailboat having a hull and a sail; a supporting assembly fixed to said hull and projecting from the windward side of said hull; and a hold-down fin assembly comprising: an elongated body member pivotably depending from said supporting assembly and disposed to pivot freely about a yaw axis and a pitch axis, a planing surface depending from said body member at the forward end thereof, a hold-down fin fixed and depending from said body member aft of said planing surface and disposed transversely to said body member, and first means fixed to said body member and responsive to the forward motion of said sailboat to maintain said planing surface forward of said hold-down fin.
 2. The combination of claim 1 wherein means are provided responsive to the forward motion thereof to maintain said planing surface in contact with the water.
 3. The combination of claim 1 wherein said first means includes a vertical fin connected between said hold-down fin and said body member.
 4. The combination of claim 3 wherein: means are provided responsive to the forward motion thereof to maintain said planing surface in contact with the water, and said hold-down fin is further mounted so that an angle between the body member and the fin is fixed so, as the sail boat tends to lift the body member, the planing surface remains in contact with the water and the angle of attack of the fin changes to increase the pulldown force.
 5. The combination of claim 4 wherein a lifting fin is disposed depending from said body member aft of said hold-down fin and disposed, in response to the forward motion thereof, to lift the aft end of said body member to maintain said planing surface in contact with the water.
 6. The combination of claim 1 wherein: second means are pivotably mounted onto the forward end of said hull and disposed to pivot downward about another pitch axis; another planing surface is mounted to the underside of said second means so that, as said second means is pivoted downward, said other planing surface forces the forward end of the hull upwards; and a transverse fin, fixed to said hull, to pivot with said hull as it pitches and disposed to be responsive to the forward motion of said hull, to lift the aft end to said hull whenever the forward end thereof is lifted.
 7. The combination of claim 6 wherein a vertical fin is fixed to the under side of said hull and said transverse fin is fixed to said vertical fin below the hull. 